Communications between distant parties have evolved with an emphasis on more personal and intimate contact between communicating parties. This emphasis is clearly noted as we observe the shift from written communications (letters and telegraphs) to voice and data communications (telephony) and on to visual communications (video-conferencing). However, even with the evolution of video-conferencing, communicants still express a need for greater intimacy.
In a typical video-conferencing configuration, the video camera and the terminal screen at a video-conferencing station are not in line with one another. Specifically, as shown in FIGS. 1A and 1B, the camera 130 is placed below or above the display screen 120, respectively. E. J. Addeo and H. Tohme, The VideoWindow Research Prototype: An Experiment with a New Form of Audio/Video Teleconferencing, 1992 SID Symposium Digest of Papers, Vol. 23, Playa del Rey, Calif.: Society for Information Display, pp. 927-930. Such placement of the camera diminishes eye-to-eye contact between video-conferencing parties. When the camera 130 is placed below the screen (as shown in FIG. 1A), a local video-conferencing party (local party) 110 gazing at the screen is perceived by a video-conferencing party (distant party) at distant video-conferencing station to be looking up and away from the distant party. If the camera 130 is placed above the screen (as shown in FIG. 1B), the local party 110 is perceived by the distant party to be looking down. Because the camera 130 and screen 120 are not in line with one another, the video-conferencing party is confronted with the dilemma of either facing the camera to appear attentive to the distant party or facing the screen to view the image of the distant party. Either choice under this disposition precludes eye-to-eye contact between video-conferencing parties.
In U.S. Pat. No. 5,117,285, entitled Eye Contact Apparatus for Video Conferencing which issued on May 26, 1992, to T. J. Nelson et al (hereafter, Patent '285), and U.S. Pat. 4,928,301, entitled Terminal with Camera Behind the Screen, which issued on May 22, 1990 to L. S. Smoot (hereafter, Patent '301), and which patents are incorporated herein by reference, the limitations associated with achieving eye-contact between parties in a video-conferencing session are discussed. Such limitations and shortcomings associated with other eye-contact schemes of the prior art often negate the intimacy and advantages gained in utilizing video-conferencing.
Placement of the camera below or above the screen as shown in FIGS. 1A and 1B also prevents the camera's field of view from overlapping with the screen's field of view as perceived by one looking through the screen. Such placement of the camera inhibits intimacy in video-conferencing and gives false visual cues because viewing reciprocity is diminished. Viewing reciprocity refers to the ability of the local party and the distant party to view one another. Therefore, viewing reciprocity exists where the local party 110 can see the distant party if the distant party can see the local party. However, if the local party and the distant party are communicating through a conventional video-conferencing system, the local party can possibly continue to view the distant party's image on the screen even when the local party moves outside of the field of view of the camera at local party's location, but the local party cannot be seen by distant party. The lack of mutual visual capability is called a reciprocity failure.
As discussed in the Backgrounds of Patents '285 and '301, in some prior eye-contact arrangements (K. Deno, Video Conferencing System for Courtroom and Other Applications," U.S. Pat. No. 4,965,819, Oct. 23, 1990), viewing reciprocity is limited due to the placement of the camera. When the camera is placed below the screen 120, as shown in FIG. 2A which depicts a top view of a prior eye-contact arrangement, the field of view of the camera 130 (shown in phantom) does not completely overlap the field of view of the screen as perceived by one looking through the screen. To cast a greater feeling of reality, the view captured by the camera and received by a distant party should replicate the view seen by one as if looking through a window defined by the screen 120. Therefore, the distant party should have a field of view defined by lines A and B as shown in FIG. 2. When the camera 130 has a narrower field of view as defined by lines A' and B', the distant party does not enjoy viewing reciprocity with the local party 110.
We refer to the regions between lines A and A' and between lines B and B' as "dead zones," since objects positioned within these regions cannot be captured by the camera 130 and thus cannot be seen by the distant party. Specifically, when the local party 110 unknowingly moves outside of the camera's field of view into the "dead zones," but still remains in front of the screen, the local party believes that he or she can still be seen by the distant party. This false perception results in confusion during video-conferencing and detracts from the feeling of reality that a video-conferencing system should optimally project.
Patent '301 reduces "dead zones" and casts a truer view of the video-conferencing station environs to the distant party by having the camera behind and in a line with the screen. An objective of Patent '301 is a new video-conferencing terminal design 300 (shown in FIG. 2B) employing a video projection source 302, a video camera 130, a half-silvered mirror 304, and a liquid-crystal screen 301. To have the video camera 130 in line with the screen, a special liquid crystal screen 301 is employed. By applying an excitation at a sufficient control voltage, the liquid crystal screen 301 can be rapidly switched, in time, from a transparent to a translucent state. This terminal operates in two modes: a capture mode and an image display mode. During the image capture mode, the liquid crystal screen is excited such that it is made transparent and the video camera 130 captures an in-line image of the local party 110. During the image display mode, the liquid crystal screen is made translucent and serves as a rear-projection screen to display the image of a distant party generated by the video projector source 302 and reflected by the half-silvered mirror 304.
The bi-modal operation of the liquid crystal display and the configuration of the terminal ensure eye-contact between communicating parties and also permit the camera 130 to be in line with the screen 301. However, in a video-conferencing system employing two such terminals, synchronization must be maintained between terminals in order to maintain effective communications and eye-contact.
The arrangement of Patent '301 offers substantial improvements over video-conferencing arrangements from the prior art. However, this arrangement requires a terminal with a large screen that has the capability of being rapidly switched from a transparent to translucent state by application of a suitable control voltage and also requires synchronization to achieve proper communication between terminals.
An object of Patent '285 is to provide a compact apparatus which establishes eye-to-eye contact between communicating parties without alteration to existing video-conferencing terminals and allows parties to realize more intimate communication during video-conferencing. That patent describes an apparatus to be mounted on a terminal screen, the apparatus comprising polarizers, mirrors, and a camera module positioned in front of the terminal screen. The components of that apparatus are arranged such that the overall protrusion of the apparatus from the terminal screen is minimal, thus minimizing the appearance of the display being deeply recessed into the terminal.
While the arrangement of Patent '285 offers substantial improvements over other video-conferencing arrangements from the prior art, the main focus of this patent was on compact design, and achieving ideal viewing reciprocity was not emphasized. The arrangement of Patent '285 is implementable in large-screen video-conferencing systems, however, this arrangement is most suitable and practical in systems having smaller displays, such as desk-top display screen. Implementing this arrangement in a large-screen video-conferencing system would require a large half-silvered mirror which could cause the image to appear somewhat recessed in the display.
An object of our invention is a video-conferencing system which allows greater viewing reciprocity, eliminates "dead zones," and thus promotes a feeling of "being there" among video-conferencing parties. A further object of our invention is to achieve eye-contact between parties during a video-conferencing session. Another object of our invention is an eye-contact mechanism for video-conferencing systems suitable for systems employing large-screens as well as desk-top displays. In addition, an object of our invention is a large video-conferencing screen which allows a camera positioned behind it to capture images through it as though the screen were transparent while simultaneously diffusing light from a rear projector as though the screen were translucent.